Systems, apparatus and methods for electric vehicle charging via a power conversion system

ABSTRACT

In one embodiment, an EV charging system includes: a plurality of first converters to receive and convert grid power at a distribution grid voltage to at least one second voltage; a high frequency transformer coupled to the first converters to receive the at least one second voltage and output at least one high frequency AC voltage; and a plurality of port rectifiers coupled to a plurality of secondary windings of the high frequency transformer, each of the port rectifiers comprising a unidirectional AC-DC converter to receive and convert the at least one high frequency AC voltage to a DC voltage. At least some of the port rectifiers may be coupled in series to provide at least one of a charging current or a charging voltage to at least one dispenser to which at least one EV is to couple.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 17/244,993, filed on Apr. 30, 2021, the content ofwhich is hereby incorporated by reference.

BACKGROUND

Power conversion systems are used to interface a variety of differentelectrical loads with a power system and any associated energy storage.Power conversion systems with transformers provide galvanic isolationand allow loads to be decoupled from distribution systems and to operateat different voltages and frequencies. However, space and energy islimited in many conversion systems.

One power conversion system of current interest is a charger that can beused to charge an electric vehicle (EV). As EVs become more prevalentand are provisioned with varying charge capabilities, there is muchinterest in EV charging systems. Currently, such charging systems arerather bulky and expensive, and can be somewhat inflexible in chargecapabilities. For wide adoption of electric vehicles, higher power fastcharging stations are needed.

SUMMARY OF INVENTION

In one aspect, an electric vehicle (EV) charging system includes: aplurality of first converters to receive grid power at a distributiongrid voltage and convert the distribution grid voltage to at least onesecond voltage; at least one high frequency transformer coupled to theplurality of first converters to receive the at least one second voltageand to electrically isolate a plurality of second converters coupled toan output of the at least one high frequency transformer; and theplurality of second converters coupled to the output of the at least onehigh frequency transformer to receive the at least one second voltageand convert the at least one second voltage to a third DC voltage. Atleast some of the plurality of second converters are to couple to one ormore EV charging dispensers to provide the third DC voltage as acharging voltage or a charging current.

In an example, the plurality of first converters are to receive thedistribution grid voltage directly from a distribution grid networkwithout an intervening power transformer. In one case, at least two ofthe plurality of second converters are to provide the charging voltageto a first EV charging dispenser. The at least two of the plurality ofsecond converters can be connected in series. The at least one highfrequency transformer may have a single primary winding and a pluralityof secondary windings, where each of the plurality of secondary windingsis to provide the at least one second voltage to one of the plurality ofsecond converters.

In an example, the EV charging system further comprises a grid-tiemodule having the plurality of first converters, the grid-tie moduledirectly coupled to a distribution grid network to receive thedistribution grid voltage. The EV charging system may further compriseat least one solar converter coupled to the at least one high frequencytransformer and at least one photovoltaic array.

In an example, the EV charging system further includes a controller, ina generation mode, to cause energy from the at least one photovoltaicarray to be provided to the distribution grid network via the EVcharging system. The controller, in a charging mode, may cause at leastsome of the energy from the at least one photovoltaic array to beprovided to the one or more EV charging dispensers. The controller, in areverse power mode, is to cause stored energy from an energy storage ofan EV coupled to the one or more EV charging dispensers to be providedto the distribution grid network.

In an example, the at least one high frequency transformer is to operateat 5 kilohertz or more. At least one of the plurality of secondconverters may receive a low voltage from a power generator coupled tothe EV charging system, the power generator to generate the low voltagefrom an ammonia-based source. At least one other of the plurality ofsecond converters may receive the low voltage from the at least one highfrequency transformer and provide the third DC voltage to the one ormore EV dispensers using the low voltage.

In an example, the EV charging system further includes a controller toobtain power telemetry information from a distribution grid network thatprovides the grid power, and based at least in part thereon, to causethe EV charging system to compensate the distribution grid network forat least one of reactive power, harmonic current, or voltage sag. The EVcharging system may integrate the one or more EV charging dispensers toenable one or more EVs to directly couple to the EV charging system.

In another aspect, an EV charging system comprises: a grid-tie module todirectly couple to a distribution grid network at a grid connection andconvert a grid voltage to a plurality of high frequency AC voltages; atleast one high frequency transformer coupled to the grid-tie module toreceive the plurality of high frequency AC voltages and to output aplurality of electrically isolated high frequency AC voltages; and aplurality of EV chargers coupled to the at least one high frequencytransformer. Each of the plurality of EV chargers may receive one of theplurality of electrically isolated high frequency AC voltages andprovide a DC voltage to at least one EV charging dispenser.

In an example, each of the plurality of EV chargers comprises at leastone output stage comprising: an AC-DC converter coupled to the at leastone high frequency transformer to receive one of the plurality ofelectrically isolated high frequency AC voltages and output a first DCvoltage; and a DC-DC converter coupled to the AC-DC converter to receivethe first DC voltage and output the DC voltage. The grid-tie module mayinclude a plurality of input stages. Each of the plurality of inputstages may comprise: an AC-DC converter to receive the grid voltage andoutput a second DC voltage; and a DC-AC converter coupled to the AC-DCconverter to receive the second DC voltage and output the high frequencyAC voltage. A first EV charger may comprise a plurality of outputstages. A controller may configure the first EV charger to cascade theplurality of output stages to provide the DC voltage comprising acharging voltage.

In an example, the at least one high frequency transformer comprises asingle transformer having a single primary winding coupled to thegrid-tie module and a plurality of secondary windings, where each of theplurality of secondary windings is coupled to one of the plurality of EVchargers.

In an example, the EV charging system further comprises a controller tocontrol a first EV charger to provide a first DC voltage at a chargingvoltage level to a first EV charging dispenser in a first mode and toprovide a second DC voltage at a charging current level to the first EVcharging dispenser in a second mode. The controller may select one ofthe first mode and the second mode based at least in part on statusinformation of an EV coupled to the first EV charging dispenser. Thecontroller may control the grid-tie module to compensate for one or moreof reactive power, harmonic current, or voltage sag.

In an example, the EV charging system further comprises a storageconverter coupled to the at least one high frequency transformer. Thestorage converter may receive energy from a storage device coupled tothe EV charging system and convert the energy to a second high frequencyAC voltage, and provide the second high frequency AC voltage to the atleast one high frequency transformer.

In yet another aspect, a method includes: receiving, in an EV chargingsystem directly coupled to a distribution grid network, a grid voltageat a grid frequency; converting, in a first input stage of the EVcharging system, the grid voltage to a first high frequency AC voltage;transforming the first high frequency AC voltage to a second highfrequency AC voltage; converting, in a first output stage of the EVcharging system, the second high frequency AC voltage to a first DCvoltage; and providing the first DC voltage to at least one EV chargingstation coupled to the EV charging system.

In an example, the method further comprises providing the first DCvoltage to a plurality of EV charging stations coupled to the EVcharging system. The method may further include: in a first mode,providing the first DC voltage at a charging voltage level to the atleast one EV charging station based at least in part on statusinformation of a first EV coupled to the at least one EV chargingstation; and in a second mode, providing the first DC voltage at acharging current level to the at least one EV charging station based atleast in part on status information of a second EV coupled to the atleast one EV charging station.

In yet a further aspect, a method includes: receiving, in an EV chargingsystem directly coupled to a distribution grid network, EV power from anEV coupled to the EV charging system; converting, in a first outputstage of the EV charging system coupled to the EV, a DC voltage of theEV power to a second high frequency AC voltage; transforming the secondhigh frequency AC voltage to a first high frequency AC voltage;converting, in a first input stage of the EV charging system coupled tothe distribution grid network, the first high frequency AC voltage to agrid voltage and a grid frequency; and providing power to thedistribution grid network from the first input stage, the power at thegrid voltage and the grid frequency.

In an example, the method further comprises: providing the power to thedistribution grid network in a reverse mode; and receiving grid powerfrom the distribution grid network and using the grid power to provide aDC voltage to at least one other EV in a forward mode.

In an example, the method further comprises: communicating informationbetween a controller of the EV charging system and the EV; based atleast in part on the information, determining that the EV is capable ofproviding the EV power; and configuring circuitry of the EV chargingsystem for the reverse mode in response to the determining.

In another aspect, an EV charging system comprises: a plurality of firstconverters to receive grid power at a distribution grid voltage andconvert the distribution grid voltage to at least one second voltage; asingle high frequency transformer coupled to the plurality of firstconverters to receive the at least one second voltage and to output atleast one high frequency AC voltage; and a plurality of port rectifierscoupled to a plurality of secondary windings of the single highfrequency transformer, each of the plurality of port rectifierscomprising a unidirectional AC-DC converter to receive the at least onehigh frequency AC voltage and convert the at least one high frequency ACvoltage to a DC voltage. At least some of the plurality of portrectifiers are coupled in series to provide at least one of a chargingcurrent or a charging voltage to at least one dispenser to which atleast one EV is to couple.

In an example, the EV charging system further comprises a solid statecircuit breaker to disable at least one of the plurality of portrectifiers. The solid state circuit breaker may comprise one or more ofthe plurality of first converters. The EV charging system may furtherinclude a controller, where the controller is to disable at least onegate signal to one or more of the plurality of first converters inresponse to detection of a fault.

In an example, the plurality of port rectifiers may be a plurality ofpassive rectifiers. And the EV charging system may further include acontroller to control at least some of the plurality of first convertersto cause the plurality of passive rectifiers to provide the at least oneof the charging current or the charging voltage. The plurality of firstconverters may each comprise a grid-side converter to convert an ACvoltage of the grid power to a DC voltage and a high frequency converterto convert the DC voltage to a high frequency AC voltage.

In an example: in a first mode, the controller is to control thegrid-side converter of the at least some of the plurality of firstconverters to cause the plurality of passive rectifiers to provide theat least one of the charging current or the charging voltage; and in asecond mode, the controller is to control the high frequency converterof the at least some of the plurality of first converters to cause theplurality of passive rectifiers to provide the at least one of thecharging current or the charging voltage.

In an example, the at least one dispenser comprises a plurality ofdispensers coupled to the plurality of unidirectional rectifiers, wherethe plurality of dispensers are to receive a fixed voltage from theplurality of unidirectional rectifiers and provide a requested chargelevel to one or more EVs. The EV charging system may further include atleast one platform coupled to the EV charging system. The at least oneplatform may include: a DC-DC converter to receive the charging voltageand output a DC charging voltage or a charging current; a plurality ofswitches coupled to the DC-DC converter; a plurality of dispensers eachcoupled to one of the plurality of switches, where each of a pluralityof EVs is to couple to one of the plurality of dispensers; and acontroller to selectively cause the DC charging voltage or the chargingcurrent to be provided to at least some of the plurality of dispensersin sequence. The controller may selectively switch the DC chargingvoltage or the charging current from being provided to a first dispenserof the plurality of dispensers to being provided to a second dispenserof the plurality of dispensers in response to at least one of atemperature of a battery of a first EV coupled to the first dispenser ora state of charge of the battery of the first EV reaching a thresholdlevel.

In another aspect, a method comprises: receiving, in a controller of anEV charging system, an indication of connection of at least one EV to adispenser coupled to the EV charging system; determining a charginglevel to be supplied to the at least one EV; and based at least in parton the charging level, controlling one or more of the plurality of firstconverters to supply the charging level to the at least one EV. In anexample, the EV charging system comprises: a plurality of firstconverters to receive grid power from a distribution network; a highfrequency transformer coupled to the plurality of first converters; anda plurality of unidirectional rectifiers coupled to the high frequencytransformer.

In an example, controlling the one or more of the plurality of firstconverters comprises sending gate control signals to a front-endconverter of the one or more of the plurality of first converters, tocause the one or more of the plurality of unidirectional rectifiers tosupply the charging level to the at least one EV. The method may furthercomprise: measuring a current at at least one of the plurality of firstconverters; measuring a voltage at at least one of the plurality offirst converters; determining a control value based at least in part onthe measured current and the measured voltage; and generating the gatecontrol signals based at least in part on the control value.

In an example, controlling the one or more of the plurality of firstconverters comprises controlling a duty cycle of a high frequencyconverter of the one or more of the plurality of first converters, tocause the one or more of the plurality of unidirectional rectifiers tosupply the charging level to the at least one EV. The method may furthercomprise: supplying the charging level to a first EV, until at least oneof a temperature of a battery of the first EV or a state of charge ofthe battery of the first EV reaches a threshold level; and thereaftersupplying the charging level to another EV. The method may furthercomprise controlling a switching network of a fleet charger comprisingthe dispenser to supply the charging level to the first EV andthereafter to supply the charging level to the another EV.

In yet another aspect, an EV charging system comprises: a grid-tiemodule comprising a plurality of grid-side converters to receive gridpower at a distribution grid voltage and convert the distribution gridvoltage to a plurality of DC voltages and a plurality of high frequencyconverters to convert the plurality of DC voltages to a plurality offirst high frequency AC voltages; a single high frequency transformerhaving: a plurality of primary windings each coupled to one of theplurality of high frequency converters to receive a corresponding one ofthe plurality of first high frequency AC voltages; and a plurality ofsecondary windings each to output one of a plurality of second highfrequency AC voltages; and a plurality of port rectifiers coupled to theplurality of secondary windings, each of the plurality of portrectifiers comprising a unidirectional AC-DC converter to receive one ofthe plurality of second high frequency AC voltages and convert the onesecond high frequency AC voltage to a DC voltage, where at least some ofthe plurality of port rectifiers are coupled together to provide atleast one of a charging current or a charging voltage; and at least onedispenser coupled to the plurality of port rectifiers, where the atleast one dispenser is to provide the at least one of the chargingcurrent or the charging voltage to at least one EV.

In an example, the EV charging system further comprises a controller tocontrol the grid-tie module to cause the at least some of the pluralityof port rectifiers to provide the least one of the charging current orthe charging voltage to the at least one EV. The controller may controla duty cycle of at least some of the plurality of high frequencyconverters to cause the at least some of the plurality of portrectifiers to provide the least one of the charging current or thecharging voltage to the at least one EV. The at least one dispenser mayprovide the at least one of the charging current or the charging voltageto the at least one EV comprising a medium duty or a heavy duty EV, tocharge the at least one EV to at least an 80% charge level withinapproximately 30 minutes or less.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram illustrating an environment in which an EVcharging system accordance with an embodiment may be used.

FIG. 1B is a block diagram illustrating another environment in which anEV charging system accordance with an embodiment may be used.

FIG. 2 is a block diagram of an EV charging system in accordance with aparticular embodiment.

FIG. 3 is a block diagram of an EV charging system in accordance withanother embodiment.

FIG. 4A is schematic diagram of an example DC-DC converter in accordancewith an embodiment.

FIG. 4B is schematic diagram of an example DC-DC converter in accordancewith another embodiment.

FIG. 5 is a schematic diagram of an example DC-DC converter inaccordance with yet another embodiment.

FIG. 6 is a block diagram illustrating an environment in which an EVcharging system in accordance with another embodiment may be used.

FIG. 7 block diagram illustrating an environment in which an EV chargingsystem in accordance with a further embodiment may be used.

FIG. 8 is a flow diagram of a method in accordance with an embodiment.

FIG. 9 is a flow diagram of a method in accordance with anotherembodiment.

FIG. 10 is a block diagram illustrating another environment in which anEV charging system accordance with an embodiment may be used.

FIG. 11 is a block diagram illustrating yet another environment in whichan EV charging system accordance with an embodiment may be used.

FIG. 12 is a flow diagram of a method in accordance with yet anotherembodiment.

FIG. 13A is a block diagram illustrating another environment in which anEV charging system accordance with an embodiment may be used.

FIG. 13B is a block diagram illustrating a still other environment inwhich an EV charging system accordance with an embodiment may be used.

FIG. 13C is a block diagram illustrating yet another environment inwhich an EV charging system accordance with an embodiment may be used.

FIG. 14 is a block diagram of an EV charging system in accordance withanother embodiment.

FIG. 15 is a schematic diagram of a power stage in accordance with anembodiment.

FIG. 16 is a schematic diagram of a port rectifier in accordance with anembodiment.

FIG. 17A is a block diagram of a controller in accordance with anembodiment.

FIG. 17B is a block diagram of a controller in accordance with anotherembodiment.

FIG. 18 is a flow diagram of a method in accordance with anotherembodiment.

DETAILED DESCRIPTION

In various embodiments, an electric vehicle (EV) charging system isprovided that enables direct connection to a grid network and generatesfrom received grid power one or more sources of charging power that canbe provided to one or more EV charging stations. In this way, EVsconnected to an EV charging station can be efficiently charged at acharging voltage and/or charging current that may be dynamicallycontrolled.

Referring now to FIG. 1A, shown is a block diagram illustrating anenvironment in which an EV charging system in accordance with anembodiment may be used. More particularly in FIG. 1A, an EV chargingsystem 100, which may be a distributed modular-based charging system,couples between a grid network 50 (represented by transmission lines 52and a distribution feeder 54) and multiple EV charging stations 60 ₁-60_(n) (also referred to herein as “dispensers”), each of which may beimplemented with one or more EV distributors to enable charging of an EV(representative EVs 65 ₁-65 _(n) are shown in FIG. 1A).

More specifically, embodiments may be used for use with distributiongrid networks that provide power at medium voltage levels (e.g., betweenapproximately 1000 volts (V) and 35000V) and at a low frequency (e.g.,50 or 60 Hertz (Hz)). For ease of discussion, understand that the terms“grid,” “grid network” or “distribution grid network” are to be usedinterchangeably to refer to a power distribution system that providesmedium voltage power at low frequency. With embodiments herein, an EVcharging system such as charging system 100 may directly couple to amedium voltage distribution grid network (which may be an AC voltagegrid or a DC voltage grid) without an intervening power transformer.Stated another way, embodiments provide an EV charging system that canbe adapted to couple to a distribution grid network without a step uptransformer, also known as a power or distribution transformer.

In this way, EV charging system 100 may directly receive incoming gridpower with a grid voltage at a medium voltage level and a low frequency.As used herein, the terms “direct connection” and “direct coupling” withrespect to an EV charging system mean that this system receivesdistribution grid power at a distribution grid network-provided gridvoltage at a distribution grid network low frequency without presence ofintervening components. Note that an EV charging system may couple to agrid network through a line reactor, a fuse, a circuit breaker, and/or apower circuit disconnect, and still be considered to be in a “directcoupling” with the grid network.

With embodiments, a means is provided for charging electric vehicles orother moving objects. In implementations, high power fast charging maybe provided for electric vehicles by connecting to a medium voltage ACor DC distribution feeder. With an EV charging system as describedherein, use of components including large magnetics components such asdistribution transformer and in-line reactors may be avoided.

Charging system 100 may be implemented as a modular facility. Stillfurther with embodiments herein in which the need for a powertransformer is avoided, EV charging system 100 may be implemented with arelatively small and low cost arrangement. For example, in embodimentsherein an EV charging system having a total apparent power of 5 megavoltamperes (MVA) may be configured in one or more modular cabinets havingapproximate dimensions of 2 meters (m)×1.6 m×2.4 m. Thus without theneed for a power transformer, an EV charging system may be readilyadapted in many different locations such as densely populated urbanareas, shopping centers, big box stores, and so forth. In addition, acharging system for EV charging stations may be designed to be powerdense and efficient. For purposes of operation, maintenance andpackaging, modular and scalable power conversion blocks may be used, andcan be the foundation for enabling advanced loads. As such, embodimentsprovide a modular, power-dense, and efficient power conversion systemfor EV charging stations.

In industrial power conversion applications, low voltage is typicallymost cost-efficient at low power levels, while medium voltage istypically superior at high power levels. With embodiments herein, apower density of an EV charging system can be up to 10× greater than anEV charging station having a power transformer (at its input) and a lowvoltage power conversion scheme. As one example, a power conversionscheme at 12470V versus 480V will require 26 times (12470V/480V=26) lesscurrent. Since conductor capacity is determined by I²R (where I iscurrent and R is resistance), an equivalent 480V charging system wouldbe required to implement conductors that are 675 times larger thanconductors for a medium voltage EV charging system in accordance with anembodiment. Continuing with this example, a 1 MW 480V charging systemmay have a rated current of approximately 1200 amperes root mean squared(Arms), whereas a 1 MW 12470V charging system in accordance with anembodiment may have a rated current of approximately 46.3 Arms.Furthermore, low voltage transformer cost/size typically increasessignificantly above 1 MVA, such that a typical maximum transformer sizefor a low voltage charging station is 1 MVA. Thus embodiments may enablelower cost, lower size, lower complexity charging stations that realizegreater charging capacity.

Still with reference to FIG. 1A, distribution feeder 54 of grid network50 may be a medium voltage AC or DC distribution feeder. As illustrated,distribution feeder 54 is directly coupled to EV charging system 100 viathree-phase connections.

Charging system 100 includes a grid-tie module 120. In embodimentsherein, grid-tie module 120 may be configured to receive grid power atan incoming grid voltage (which as described above may be an AC or DCvoltage) and perform an initial conversion of the incoming grid voltageto a voltage that is at different magnitude and/or frequency. Dependingon implementation, grid-tie module 120 may convert the incoming gridvoltage to one or more DC or AC voltages at different magnitude orfrequency. To this end, grid-tie module 120 interfaces with mediumvoltage AC or DC grid network 50 and utilizes power electronicsconverters to convert the AC or DC grid voltage to a voltage that is atdifferent magnitude and/or frequency. Grid-tie module 120 may includemultiple stages that may be isolated from each other. In otherimplementations, at least some of these stages may be cascaded togetherto increase voltage capabilities.

In particular embodiments herein, grid-tie module 120 may include powerelectronics-based converters to convert the incoming AC or DC gridvoltage. As an example, grid-tie module 120 may include so-calledH-bridge power converters to receive the incoming grid voltage andperform a voltage/frequency conversion, e.g., to a DC voltage. In turn,grid-tie module 120 may further include a first stage of a DC-DCconverter to convert the DC voltage to a high frequency AC voltage(e.g., a square wave voltage) at a given high frequency (e.g., between 5kilohertz (kHz) and 100 kHz).

As further illustrated in FIG. 1A, this high frequency AC voltage may beprovided to a transformer network 130. In the embodiment shown in FIG.1A, transformer network 130 includes multiple isolated transformers,each having a single primary winding and a single secondary winding. Inother implementations a transformer network may take the form of asingle transformer having a single primary winding and multiplesecondary windings.

In either case, transformer network 130 is configured as a highfrequency transformer. In embodiments, transformer network 130 mayoperate at frequencies between approximately 5 kHz and 100 kHz. Byvirtue of this high frequency of operation, the need for large magneticsat a front end can be avoided. In one implementation transformer network130 may have a size of less than approximately 1 m×1 m×0.25 m.Transformer network 130 outputs galvanically isolated AC voltages. Inthis way, transformer network 130 provides electrical isolation betweendistribution feeder 54 and EV charging stations 60.

Still referring to FIG. 1A, the secondary windings of transformernetwork 130 each may be coupled to an electrically isolated vehiclecharger 140 ₁-140 _(n). In embodiments herein, each vehicle charger 140may be configured as a power electronics converter that converts thesecondary voltage output by transformer network 130 to a voltage (e.g.,DC) at a different frequency and/or magnitude. More particularly forvehicle charging as described herein, vehicle chargers 140 may includeDC-DC converters to provide charge capabilities to at least one EVcharging station 60.

Continuing with the above discussion in which an AC voltage is outputfrom transformer network 130, vehicle chargers 140 may include an AC-DCconverter as well as a DC-DC converter to provide charging capability ata desired charging voltage and/or charging current.

As shown in FIG. 1A, EV charging system 100 may be coupled to chargingstations 60 via a plurality of output lines 551-n. Although differentconnection topologies are possible (including direct connection as shownin FIG. 1B, discussed below), FIG. 1A shows an implementation in whicheach output line 55 is dedicated to a single charging station 60.

To effect control of EV charging system 100, at least one controller 150may be present. In various embodiments, controller 150 may include oneor more central processing units (CPUs) or systems on chip (SoCs), adedicated microcontroller or other programmable hardware control circuitsuch as programmable logic. In one embodiment, controller 150 may form adistributed control architecture. In any case, controller 150 may beconfigured to execute instructions stored in one or more non-transitorystorage media. Such instructions may cause controller 150 toautomatically and dynamically control charging voltages and/or chargingcurrents depending upon capabilities and requirements of chargingstations 60 and/or connected EVs 65.

Controller 150 may be configured to control, in addition to one or moreconfigurable charging modes, one or more generation and/or storagemodes, in which energy stored in one or more batteries of an EV may bestored within a storage within or coupled to EV charging system 100(such as one or more batteries (not shown for ease of illustration inFIG. 1A)) or provided as energy to the grid, e.g., via connection todistribution feeder 54, as will be described further herein.

Although shown with this particular implementation in the embodiment ofFIG. 1A, many variations and alternatives are possible. For example, anEV charging system may be configured to directly connect to EVs.Referring now to FIG. 1B, shown is a block diagram illustrating anotherenvironment in which an EV charging system in accordance with anembodiment may be used. More particularly in FIG. 1B, an EV chargingsystem 100′ may be configured the same as system 100 of FIG. 1A, withthe sole difference being that system 100′ provides vehicle chargingconnectors integrated therein such that output lines 55 and chargingstations 60 may be eliminated. Thus as shown in FIG. 1B, system 100′,via chargers 140 and integrated charging connectors, directly connect toEVs 65.

In still further implementations an EV charging system also may includecapabilities to provide load power to a variety of AC loads, such asindustrial facilities or so forth. In addition, the EV charging systemmay be configured to receive incoming energy, such as from one or morephotovoltaic arrays or other solar panels and provide such energy,either for storage within the EV charging system, distribution to thegrid and/or as charging power to connected EVs.

As described above, different configurations of EV charging systems arepossible. Referring now to FIG. 2, shown is a block diagram of an EVcharging system in accordance with a particular embodiment. As shown inFIG. 2, EV charging system 200 is a multi-port modular power converterthat uses a single transformer. In FIG. 2, understand that a singlephase is illustrated for ease of discussion. In a given charging systemthere may be three phases, each configured as shown in FIG. 2 orcombined as a single transformer.

Incoming grid power is received at a given grid voltage via input nodes205 _(a), 205 _(b). Although embodiments are not limited in this regard,in FIG. 2 this grid voltage may be received as a medium AC voltage,e.g., at a voltage of between approximately 1 and 50 kilovolts (kV) andat a grid frequency of 50 Hz or 60 Hz. As shown, an input inductancecouples to input node 205 _(a).

The incoming voltage is provided to a plurality of input stages, each ofwhich may include multiple H-bridge converters. More specifically, aplurality of input stages 210 ₁-210 _(n) are shown that are cascadedtogether. Each input stage may include a grid-side converter 212 _(1-n)(shown as an AC-DC converter). In turn each grid-side converter 212couples to a DC-AC converter 214 ₁-214 _(n) of a given DC-DC converter215 ₁-215 _(n). Thus each grid-side converter 212 receives an incominggrid AC voltage and converts it to a DC voltage, e.g., at the same ordifferent voltage magnitude. While embodiments may typically implementconverters 212 and 214 (and additional converters described below) thatare symmetric, it is also possible for there to be asymmetricconfigurations across power stages.

In an embodiment, each grid-side converter 212 may be implemented as anH-bridge converter including low voltage or medium voltage switches,e.g., silicon carbide (SiC) devices. In other embodiments, eachgrid-side converter 212 may be formed as a multi-level rectifier. Theresulting DC voltages are in turn provided to corresponding DC-ACconverters 214 that act as an input stage of an isolated DC-DC converter215. In embodiments, converters 214 may be implemented as H-bridgeconverters to receive the DC voltage and convert it to a high frequencyAC voltage, e.g., operating at a frequency of up to 100 kHz. While asquare wave implementation is shown in FIG. 2, understand that in othercases the AC voltage may be sinusoidal.

The high frequency voltage output from converters 214 may be provided toa corresponding primary winding of a transformer 220, namely a highfrequency transformer. While shown in FIG. 2 as a single transformerwith multiple primary windings and multiple secondary windings, in otherimplementations separate transformers may be provided, each with one ormore primary windings and one or more secondary windings.

In any event, the galvanically isolated outputs at the secondarywindings of transformer 220 may be provided to a plurality of outputstages 230 ₁-230 _(o). As such each output stage 230 includes an AC-DCconverter 232 ₁-232 _(o) (of a DC-DC converter 215). Thereafter, theoutput DC voltage may be further adjusted in magnitude in correspondingload-side converters 235 ₁-235 _(o) (and 235 ₁-235 _(o)).

As illustrated, output stages 230 thus include a given output stage(namely stage 232) of a DC-DC converter 215 and a load-side converter235. As shown in FIG. 2, multiple output stages 230 may couple togetherin cascaded fashion (e.g., either in a series connection as shown inFIG. 2 or in a parallel connection) to provide a higher output voltageand/or current depending upon load requirements. More specifically, afirst set of output stages 230 ₁-230 _(m) are cascaded together andcouple to output nodes 245 _(a,b). In turn, a second set of outputstages 230 ₁-230 _(o) are cascaded together and couple to output nodes245 _(1,o). The resulting outputs are thus at a given DC voltage leveland may be used as a charging voltage and/or current for connected EVs.While this particular arrangement with cascaded input and output stagesare shown in FIG. 2, understand that a multi-port power converter may beimplemented in other manners such as using modular high frequencytransformers. Still further, understand that the actual included DC-DCconverters may have a variety of different topologies.

For example, in other cases a modular high frequency transformer may beused. Referring now to FIG. 3, shown is a block diagram of an EVcharging system in accordance with another embodiment. As shown in FIG.3, EV charging system 300 is a multi-port modular power converter thatuses a modular transformer. As in FIG. 2, a single phase is illustratedfor ease of discussion.

Incoming grid power is received at a given grid voltage via input nodes305 a, 305 b. The incoming voltage is provided to a plurality of inputstages, each of which may include multiple H-bridge converters. Morespecifically, a plurality of power converter stages 310 ₁-310 _(n) areshown. Each stage 310 may include a grid-side converter 312 _(1-n)(shown as an AC-DC converter) and a DC-AC converter 314 ₁-314 _(n) of agiven DC-DC converter 315 ₁-315 _(n). Via independent transformers ofDC-DC converters 315, a resulting electrically isolated DC voltage isprovided to an AC-DC converter 332 ₁-332 _(n) and thereafter to aload-side converter 334 ₁-334 _(n). Note that operation may be similarto that discussed in FIG. 3. In one embodiment, each load-side converter334 ₁-334 _(n) may provide a voltage to the load, e.g., connectedelectric vehicles. However here note that potentially different amountsof load-side converters 334 may be cascaded to provide a given DCvoltage to a load (e.g., EV charging station). As one example, a firstset of load-side converters 334 ₁-334 _(j) may provide a first chargingvoltage of approximately 1500 volts via output nodes 345 a,b. And asecond set of load-side converters 334 _(j+1)-334 _(n) may provide asecond charging voltage of approximately 1000 volts via output nodes 345c,d.

Referring now to FIG. 4A, shown is a schematic diagram of an exampleDC-DC converter in accordance with an embodiment. As shown in FIG. 4A,DC-DC converter 400 is implemented as a dual active bridge (DAB)isolated DC-DC converter. In various implementations, converter 400 maybe used in a multi-port modular power converter such as those shownabove in FIGS. 2 and 3 and/or other EV charging systems.

In the high level shown in FIG. 4A, converter 400 includes an inputstage 410 having a plurality of SiC switches Tp1-Tp4. As shown, switchesTp1-Tp4 are implemented in an H-bridge configuration and couple to inputnodes 405 a,b that receive an incoming DC voltage Vdcp. As shown, aparallel capacitance Cp couples between the input nodes. In turn, themidpoints between serially coupled SiC switches Tp1, Tp2 and Tp3, Tp4couple to an input winding, namely a primary winding of a high frequencytransformer 420. In embodiments herein, high frequency transformer 420may be configured to operate at frequencies between approximately 5 kHzand 100 kHz.

Still in reference to FIG. 4A, the secondary winding of high frequencytransformer 420 in turn couples to the midpoints of serially connectedSiC switches Ts1, Ts2 and Ts3, Ts4 of an output stage 430. Asillustrated, output stage 430 further includes a capacitance Cs coupledbetween output ports 435 a,b that provide an output DC voltage Vdcs. Itis noted that switches Tp1-Tp4 and Ts1-Ts4 can be any type of powersemiconductor switches including Silicon (Si) or Silicon Carbide (SiC),Gallium Nitrite (GaN) metal oxide semiconductor field effect transistors(MOSFETs) or insulated gate bipolar transistors (IGBTs).

With this arrangement implementing SiC or other high speed silicon powerswitches, improved conversion efficiency may be realized as a result oflower switching losses. In one implementation, SiC devices as in FIG. 4Amay be implemented with low voltage switches such as 1700V SiC MOSFETs.Use of low voltage switches reduces the stress on insulation, dv/dt andparasitic capacitances, along with high reliability.

In addition, thermal management may be simplified, e.g., resulting insmaller and less expensive heat sinks or cooling systems, and/orreplacement of fluid/forced air with natural cooling. Still further withembodiments, passive components (inductors, capacitors) may be downsizedat higher switching frequencies. For example, with reference back toFIG. 4A, the input and output side capacitances may be on the order ofapproximately 40 microFarads. Also with a DAB design as in FIG. 4A, apower converter may be realized with greater simplicity andcontrollability, low switching losses, low sensitivity to systemparasitic elements, bidirectional power flow, and the possibility toachieve Zero Voltage Switching (ZVS) for all semiconductors to allow fora high switching frequency and efficiency.

Referring now to FIG. 4B, shown is a schematic diagram of an exampleDC-DC converter in accordance with another embodiment. As shown in FIG.4A, DC-DC converter 400′ may be have a front end implemented the same asconverter 400 of FIG. 4A. however here, the secondary side isimplemented with passive devices, namely diodes Ds1-Ds4. With thisimplementation, power flow is unidirectional from grid to EV's, suchthat reverse power flow from EV to grid does not occur here.

In another embodiment, a DC-DC converter may take the form of a T-typebidirectional isolated DC-DC converter. Referring now to FIG. 5, shownis a schematic diagram of an example DC-DC converter in accordance withyet another embodiment. While formed of SiC devices, note the topologyin FIG. 5 has SiC devices Tp1 and Tp2 coupled in series between inputnodes 505 a,b, and SiC devices Tp3 and Tp4 coupled in series between aninput winding of a transformer 510 and input capacitors Cp1, Cp2.Similarly an output stage 530 has a T-type arrangement of SiC devicesTs1-Ts4 that providing switching between a secondary winding oftransformer 520 and output nodes 535 a,b having an output capacitanceCs1, Cs2 coupled therebetween. As above, switches Tp1-Tp4 and Ts1-Ts4can be any type of power semiconductor switches including Si, SiC,and/or GaN MOSFETs or IGBTs. Of course other implementations of DC-DCconverters are possible in other embodiments.

Referring now to FIG. 6, shown is a block diagram illustrating anenvironment in which an EV charging system in accordance with anotherembodiment may be used. More particularly in FIG. 6, an EV chargingsystem 600 may be generally similarly configured the same as EV chargingsystem 100 of FIG. 1A (and thus reference numerals generally refer tothe same components, albeit of the “600” series in place of the “100”series of FIG. 1A). However in this embodiment, system 600 includes atleast one DC-AC load converter 635 to provide AC power to a facility670. As further shown, system 600 also includes a solar converter 638that may couple to a solar photovoltaic panel 680. In this way, incomingsolar energy can be provided to grid network 650, to EV chargingstations 660 and/or stored in an energy storage (such as a batterysystem of system 600 (not shown for ease of illustration in FIG. 6)).Thus with this embodiment, EV charging system 600 may couple to one ormultiple AC or DC loads and/or to one or multiple solar photovoltaicpanels.

Still further implementations are possible. For example, isolatedvehicle charger section can interface with multiple EV chargingdispensers. Referring now to FIG. 7, shown is a block diagramillustrating an environment in which an EV charging system in accordancewith a further embodiment may be used. More particularly in FIG. 7, anEV charging system 700 may be generally similarly configured the same asEV charging system 100 of FIG. 1A (and thus reference numerals generallyrefer to the same components, albeit of the “700” series in place of the“100” series of FIG. 1A). However in this arrangement, EV chargingsystem 700 may be configured such that a single vehicle charger 740couples via output lines 755 to multiple EV charging dispensers 760.

In yet other embodiments, an EV charging system may provide volt-amperereactive power compensation to a utility that enables maximum power tobe delivered to the charging system without exceeding distributionfeeder capacity.

Referring now to FIG. 8, shown is a flow diagram of a method inaccordance with an embodiment. As shown in FIG. 8, method 800 is amethod for controlling an EV charging system in accordance with anembodiment. As an example, method 800 may be performed by an EV chargingsystem such as any of those described above. In part, method 800 may beexecuted using instructions stored in one or more non-transitory storagemedia such as may be executed by a hardware circuit (e.g., a CPU, SoC,microcontroller, or so forth). In other implementations, a purehardware-based arrangement may be present in which an EV charging systemis hard-wired for a particular configuration. And of course, varyingdegrees of programmability and configurability may be present indifferent implementations.

As illustrated, method 800 begins by receiving grid power at a gridvoltage and a grid frequency (block 810). In an embodiment, this gridpower (at medium voltage) may be directly received from a distributiongrid network in a grid-tie module of an EV charging system. Next atblock 820 the grid voltage is converted to a first high frequency ACvoltage. More particularly, in an input stage, e.g., of the grid-tiemodule, the incoming grid voltage (e.g., at a voltage up to 50 kV and ata grid frequency of 50 Hz or 60 Hz) may be converted to an AC voltage ata frequency between approximately 5 kHz and 100 kHz.

Still referring to FIG. 8, next at block 830 this first high frequencyAC voltage is transformed to a second high frequency AC voltage. Notethat this transformation, which may be performed in one or more highfrequency transformers, acts to provide electrically isolated highfrequency AC voltages to different EV chargers. Then at block 840 thesecond high frequency AC voltage is converted to a DC voltage. Morespecifically, in an output stage, e.g., of an EV charger, the secondhigh frequency AC voltage is converted to a DC voltage at a givencharging voltage and/or current. Finally, at block 850 this DC voltageis provided to one or more EV charging stations that may use the voltageto charge one or more connected EVs.

Note that the level of the DC voltage and its provision for charging oneor more connected EVs may be based at least in part on communicationswith the EV. For example, when an EV is plugged into an EV chargingsystem with minimal charge remaining in its battery (and communicatesstatus information including its current capacity) the controller maycause the DC voltage to be provided as a charging current to realizefaster charging. Then when the battery is closer to a full charge (andupdated status information is communicated), the controller may causethe DC voltage to be provided as a charging voltage to complete thecharge. Understand while shown at this high level in the embodiment ofFIG. 8, many variations and alternatives are possible.

Further understand that in different implementations, an EV chargingsystem may provide fast charging higher power levels, resulting in fastcharging with potentially dramatically reduced charge times. As oneexample, an extreme fast charging system in accordance with anembodiment may operate a power levels of 350 kiloWatts (kW) or more, andbe capable of effecting a charge time of approximately 15 minutes orless for a 200 mile capacity. In contrast, conventional EV fast chargersthat operate up to approximately 140 kW may incur over 35 minutes for anequivalent charge. Thus embodiments that directly couple to a mediumvoltage distribution grid may provide significantly faster chargingtimes, with a smaller, cheaper charging system.

In many regions, the cost of electricity varies with conditions,including demand. Oftentimes, electricity is cheaper at night thanduring at least certain hours of the day. Some consumers having EVs maytake advantage of this situation by charging their EV at night (e.g.,using a low voltage home charger) when costs are lower. Then whenelectricity prices are higher during peak demand hours (e.g., daytime),a consumer may choose to discharge stored energy from the EV to thegrid, e.g., via an EV charging system in accordance with an embodiment.

As such, embodiments may provide a mechanism for reverse power flow froman EV to a grid via an EV charging system that can be dynamicallyre-configured to provide at least partial reverse power flow. Forexample, one or more EVs may couple to an EV charging system to providethis power flow while at the same time, one or more other EVs coupled tothe EV charging system receive charging power (e.g., in a fast chargingmode at high power levels).

Referring now to FIG. 9, shown is a flow diagram of a method inaccordance with another embodiment. More specifically, method 900 ofFIG. 9 is a method for providing a reverse power flow, namely from abattery or other energy storage device(s) of one or more EVs to adistribution grid. As such, method 900 may be performed by an EVcharging system such as any of those described above. In part, method900 may be executed using instructions stored in one or morenon-transitory storage media such as may be executed by any form ofcontroller (such as described in FIGS. 1A and 8, for example).

As illustrated, method 900 begins by receiving EV power at an outputstage of an EV charging system from one or more EVs (block 910). As aninitial matter, note that prior to this reverse power flow, there areinitial communications between the EV and the EV charging system (andmore specifically, with the controller of the EV charging system) toprovide capability information, including a desire to participate inthis reverse power flow, battery status information, among potentiallyadditional information such as safety status information (e.g., powerconnector engaged, vehicle ready, electrical insulation detection) andso forth. In turn, the controller may confirm that the EV is capable ofsuch reverse power flow and determine appropriate parameters for thispower delivery. Accordingly, the controller may configure, e.g.,switching circuitry of an output stage of the EV charging system toreceive this EV power and additional circuitry of the EV charging systemto direct this power flow to an appropriate destination.

Still in reference to FIG. 9, next at block 920 this incoming DC voltageof the EV power may be converted in a load-side converter to a secondhigh frequency AC voltage in the output stage. Such operation mayproceed in a reverse direction as described above such that the incomingDC voltage is converted to an AC voltage at a given high frequency(e.g., 50 kHz). Thereafter, this second high frequency AC voltage istransformed to a first high frequency AC voltage in a transformernetwork of the EV charging system (block 930).

Still referring to FIG. 9, next at diamond 940 it may be determinedwhether this reverse power flow is intended to be provided to the grid.This determination may be based on a configuration setting of the EVcharging system, either statically or dynamically. Such determinationmay be based on considerations as to whether the grid network is in needor desire of receiving such power. If so, control passes to block 950where the first high frequency AC voltage can be converted to a gridpower level. More specifically, the grid-tie module may provide thefirst high frequency AC voltage to a grid power level at a grid voltageand grid frequency. Thereafter, via the grid-tie module of the EVcharging system, this grid power is provided to the distribution gridnetwork (block 960).

In other cases it is possible for the reverse power flow received froman EV to be provided as charging power to one or more other EVs alsoconnected to the EV charging system. In this instance, the control flowfrom diamond 940 instead proceeds to block 970. There, a first highfrequency AC voltage (at the transformer network input side) istransformed to a second high frequency AC voltage (at the transformernetwork output side). Then at block 980 the second high frequency ACvoltage is converted to a DC voltage. More specifically, in an outputstage, e.g., of an EV charger, the second high frequency AC voltage isconverted to a DC voltage at a given charging voltage and/or current.Finally, at block 990 this DC voltage is provided to one or more EVcharging stations that may use the voltage to charge one or moreconnected EVs. Understand that in various use cases, one or more EVs cansupply power to the grid while at the same time one or more other EVsmay receive power from the grid, such that the grid supplies adifference between received and provided power. Understand that whileshown at this high level in the embodiment of FIG. 9, variations andalternatives are possible.

Referring now to FIG. 10, shown is a block diagram illustrating anenvironment in which an EV charging system in accordance with anotherembodiment may be used. More specifically as shown in FIG. 10, the EVcharging system 1000 may be generally configured the same as EV chargingsystem 100 of FIG. 1A (and thus reference numerals generally refer tothe same components, albeit of the “1000” series in place of the “100”series of FIG. 1A). However, in this embodiment, note that EV chargingsystem 1000 further includes a battery storage converter 1080. As shown,battery storage converter 1080 couples to a battery energy storage 1070.Note that while battery energy storage 1070 is a separate componentcoupled externally to EV charging system 1000, in other implementationsbattery energy storage 1070 may be included internally to EV chargingsystem 1000.

In embodiments herein, battery storage converter 1080 may be configuredto receive power from storage 1070 at a given DC voltage, and perform aconversion to an appropriate high frequency AC voltage, such that thisvoltage can be provided to transformer network 1030 and then in turn beprovided to one or more EV chargers 1040 for use in generating a DCvoltage for provision to a given EV charging station 1060. Of course itis possible to instead provide such battery power to distribution grid1050 via a reverse flow technique such as discussed above, in othercases.

Note that depending on configuration, the received energy can betransformed and passed through to grid-tie module 1020 before beingconverted and directed to one or more EV charging stations 1060. Suchoperation may occur where there are multiple independent transformers asshown in FIG. 10. In an implementation with a single transformer, itsmagnetic circuitry may be sufficient that the transformed AC voltagefrom one secondary winding can be directed to one or more othersecondary windings and without being passed to grid-tie module 1020.

Referring now to FIG. 11, shown is a block diagram illustrating anenvironment in which an EV charging system in accordance with anotherembodiment may be used. More specifically as shown in FIG. 11, EVcharging system 1100 may be generally configured the same as EV chargingsystem 100 of FIG. 1A (and thus reference numerals generally refer tothe same components, albeit of the “1100” series in place of the “100”series of FIG. 1A). However, in this embodiment, note that EV chargingsystem 1100 further includes an power converter 1185. As shown, powerconverter 1185 couples to a power generator 1180.

Power generator 1180 may be configured to generate a low voltage AC orDC voltage. More particularly in embodiments, power generator 1180 maygenerate an output voltage at approximately 480 volts. As shown, powergenerator 1180 may generate power from a given energy source, which inthis case is an ammonia/hydrogen source 1170.

In the embodiment of FIG. 11, power converter 1185 may convert thisincoming voltage to an appropriate high frequency AC voltage, such thatthis voltage can be provided to transformer network 1130 and then inturn be provided to one or more EV chargers 1140 for use in generating aDC voltage for provision to a given EV charging station 1160. Of courseit is possible to instead provide such low voltage power via a reverseflow technique such as discussed above to distribution grid 1150 inother cases.

Along with the increasing of electricity load type and capacity such asin connection with EV charging as described herein, power qualityissues, especially reactive power and harmonics, may affect reliableoperation of a power grid. Various control mechanisms may be used tocompensate for such power quality issues. In contrast to conventionalmechanisms which use additional components, no further components areneeded. That is, conventional techniques to control reactive power in agrid network use a static synchronous compensator, which is a dynamicshunt compensator, or a static VAR compensator.

Instead with embodiments, a compensation control mechanism caneffectively compensate the reactive power, suppress harmonic currentsand provide voltage support for a grid network to which an EV chargingsystem is coupled. Embodiments thus can provide charging power tomultiple EVs, while concurrently improving power quality of the gridnetwork, by effective reactive power and harmonics compensation at agrid connection. Thus a grid-tie module can exchange reactive power intoa grid network to provide reactive power compensation at the gridconnection. Such operation may occur concurrently with active power flowfrom the grid network to connected EVs or injection of reactive powerinto grid network. Accordingly, an EV charging system in accordance withan embodiment may provide dynamic reactive power compensation whileconcurrently providing charging power to one or more EVs.

More specifically, fast feedbacks and control loops, in combination withhigh speed switches of input and output stages, enable rapidcompensation for reactive power and suppress harmonic currents. To thisend, a controller may, based on feedback information, control phaseshifting of the voltage of grid-side converters (e.g., converters 212_(1-n) in FIG. 2) of the inputs to one or more transformers of atransformer network, by appropriate control of switching devices ofinput stages within a grid-tie module.

In addition, embodiments can act quickly to supply reactive power tocorrect voltage sag (voltage dip) caused by temporary events includingshort circuits, overloads and starting electric motors. As an example,voltage sag may occur when RMS voltage decreases between approximately10-90% of nominal voltage for one-half cycle to one minute. When avoltage sag is detected, a quick response can occur without the need forexternal compensation components. To this end, a controller may providereactive power to accommodate for this condition by appropriate controlof the voltage phase shift of the grid side converters within the inputstages of transformer networks.

Referring now to FIG. 12, shown is a flow diagram of a method inaccordance with yet another embodiment. As shown in FIG. 12, method 1200is a method for providing compensation to a distribution grid networkvia an EV charging system. As such, method 1200 may be performed by anEV charging system such as any of those described above. In part, method1200 may be executed using instructions stored in one or morenon-transitory storage media such as may be executed by any form ofcontroller (such as described in FIGS. 1A and 8, for example).

As shown, method 1200 begins by receiving telemetry information from agrid network (block 1210). Next it is determined at diamond 1220 whetherthe grid is operating within at least a threshold of variousrequirements. Although embodiments are not limited in this regard, suchrequirements may include reactive power requirements, voltage sagrequirements or so forth. If the grid is determined not to be operatingwithin a threshold, control passes to block 1230. At block 1230,compensation parameters may be determined. More specifically, acontroller may determine one or more compensation parameters based atleast in part on the telemetry information. These compensationparameters may include, for example, a reactive power compensationpercentage of total kiloVolt Ampere (kVA), or so forth.

Still in reference to FIG. 12, next control passes to block 1240 wherethese one or more compensation parameters may be provided to the inputstages of a grid-tie module of the EV charging system. Note that thesecompensation parameters may be used to control switching devices withinthe grid-tie module. As such, by such configuring/re-configuring ofvarious devices within the grid-tie module, at block 1250 the system mayprovide compensation for reactive power and/or harmonic currentcompression using the one or more compensation parameters. Understandwhile shown at this high level in the embodiment of FIG. 12, manyvariations and alternatives are possible.

As discussed above, EV charging systems may have different types ofconfigurations. In some cases, an EV charging system may be implementedwith an architecture that is dedicated only for providing charging toEVs. Such systems may have reduced costs and more simplified controlarrangements. In some cases, these systems may be applicable for usewith heavy and medium duty EVs. Heavy and medium duty EVs can havestorage capacities ranging from 150 kWH to over 800 kWH. These EVs needcharging systems that are designed to continuously supply high rates ofDC power, e.g., from 250 kW to 1.5 MW on a continuous basis, with atarget of 80% charge in 30 minutes.

Referring now to FIG. 13A, shown is a block diagram illustrating anotherenvironment in which an EV charging system in accordance with anembodiment may be used. More specifically in FIG. 13A, an EV chargingsystem 1300 couples between a grid network 1350 (represented bytransmission lines 1352 and a distribution feeder 1354) and multiple EVcharging stations 1360 ₁-1360 _(n) (dispensers 1360) each of which maycouple to one or more EVs 1365 _(1-n).

As illustrated in FIG. 13A, EV charging system 1300 may generally beconfigured similarly to EV charging system 100 of FIG. 1A (and thusreference numerals generally refer to the same or similar components,albeit of the “1300” series in place of the “100” series of FIG. 1A).

However in this implementation, a transformer 1330 is implemented as asingle high frequency transformer having multiple primary windings andmultiple secondary windings. Each set of secondary windings in turn maycouple to a corresponding unidirectional rectifier 1340 ₁-1340 _(n). Byproviding unidirectional rectifiers 1340, power flow occurs only in asingle direction, namely from charging system 1300 to connected EVs 1365as a given charging voltage or charging current.

Thus EV charging system 1300 couples directly to a distribution networkand provides a regulated fixed DC voltage to one or more dispensers1360. In one or more embodiments, dispensers 1360 may receive a fixed DCvoltage (e.g., at 1000V) and provide an appropriate charge voltage orcharge current as requested by each EV 1365. Note that dispensers 1360may provide electrical isolation between each EV 1365.

Other implementations may be used to provide high rates of chargingpower. Referring now to FIG. 13B, shown is a block diagram of an EVcharging system in accordance with another embodiment. In FIG. 13B, EVcharging system 1301 may generally include similar components asdiscussed above regarding FIG. 13A, and thus are shown with the samereference numbers as used in FIG. 13A, and such components are notfurther discussed. While shown as a single EV charger rectifier 1340,understand that EV charger rectifier 1340 may be formed of multiplerectifiers that are fed by different secondary windings of transformer1330, and may be coupled in series or parallel.

In addition in this implementation, charging system 1301 includes anintegrated dispenser (not separately shown) to which a medium or heavyduty EV 1365 may couple. As one example, charging system 1301 may beused for highway truck charging. With this arrangement, grid-tie module1320 couples directly to a distribution grid at distribution voltagelevels. Or in other implementations a dispenser can be placed at adistance. EV charging system 1301 may control the charge voltage orcharge current via appropriate control of grid-tie module 1320, asdescribed in more detail below.

Yet other implementations are possible. Referring now to FIG. 13C, shownis a block diagram of an EV charging system in accordance with yetanother embodiment. As shown in FIG. 13C, charging system 1302 maygenerally take the same form as in FIG. 13A, and thus is shown with thesame reference numbers as used in FIG. 13A. However here, chargingsystem 1302 provides for fleet EV charging. In this implementation, aplurality of charging platforms 1370 ₁-1370 _(n) are coupled to receivea fixed DC voltage (e.g., 1500V) output from charging system 1302.

As shown with regard to representative charging platform 1370 ₁,included is a DC/DC converter 1372 to which a plurality of switches (SW#1-SW #m) may couple. As such, EV charger DC/DC converter 1372 is sharedamong multiple EV dispensers 1360. As illustrated, each switch couplesto a corresponding dispenser 1360 _(1-m) to which a given EV 1365 (partof a EV fleet) may be coupled. EV charger DC/DC converter 1372 mayprovide isolation and a charging voltage or charging current requestedby EV 1365

In this embodiment, charging system 1302 may provide a low-cost solutionfor fleet EV charging. The configuration can charge m×n EVs (where m isthe number of dispensers per platform, and n is the number of platforms)during off duty (e.g., overnight). In operation, switches SW can switchon dispensers 1360 to charge EVs 1365 in sequence. The switches can bein the form of contactors, circuit breakers, or solid-state switches,and may be integrated in the dispenser or placed in another locationwithin platform 1370. Using this configuration minimizes the requiredpower rating of converters since the vehicles may charge in sequence.For example, charging system 1302 can be rated at 900 kW that provides600 A at 1500V DC. The EV charger DC/DC converter 1372 power rating canbe 150 kW that can provide a maximum of 150 kW of power to EV 1365 thatis being charged by selection of a given switch SW

Furthermore a controller (e.g., a programmable logic controller) maycontrol the charging functions of platforms 1370 based on temperature ofEV battery or state of charge to optimize the battery life and/orcharging times. This is so, since when the EV battery temperature rises,an EV slows down the charging to permit the battery to cool down, whichmay lengthen the charging time or reduce the life of the battery. Byswitching the charging between EV's 1365 of a platform based ontemperature and/or state of charge, speed of charging in a platformincreases and the life of the battery may extended.

Understand that variations and modifications of implementations of theembodiments described herein may lead to other fleet chargingconfigurations. For example, a dispenser can have multiple chargingcables (one or more charging cables that each cable may connect to eachEV). In turn, some type of switching mechanism may reside inside thedispenser, and may be configured to reroute power to provide chargevoltage (or charge current) sequentially, and/or based on batterytemperature and/or state of charge, to EV's connected to each dispenser.Thus in one or more embodiments, a fleet charging station may havemultiple platforms, with each platform having an EV charger DC/DCconverter and one or more dispensers. Each dispenser can have multiplecharging cables connected to multiple EVs. A switching mechanism may beconfigured to provide the required charge to each EV at a time. In anembodiment, to charge N EV's, there may be N switches. Depending onimplementation, the switches that reroute the charge to each dispensermay reside in the EV charger enclosure, or in a separate enclosurewithin a platform or inside the dispenser. Switches that switch thepower between the charging cables of a dispenser can be installed withinthe dispenser.

Referring now to FIG. 14, shown is a block diagram of an EV chargingsystem in accordance with another embodiment. As shown in FIG. 14, EVcharging system 1400 may be implemented similarly to EV charging system200 of FIG. 2 (and thus reference numerals generally refer to the sameor similar components, albeit of the “1400” series in place of the “200”series of FIG. 2). On an input side of a multi-winding transformer 1420,each input phase includes n power stages 14101-n that are connected inseries. Each power stage 1410 includes an AC/DC converter 1412, DC bus,and a DC-to-high frequency converter 1414 (also referred to as a “highfrequency converter”).

In this implementation, output stages are implemented as port rectifiers1430 ₁-1430 _(m). As shown, each port rectifier 1430 includes at leastone AC-DC converter (e.g., AC-DC converters 1432 ₁-1432 _(m)). Asillustrated in FIG. 14, multiple port rectifiers 1430 can couple inparallel to provide higher a charging current at output nodes 1445_(A,B). In other cases, port rectifiers 1430 may be coupled in series toprovide a higher charging voltage.

Referring now to FIG. 15, shown is a schematic diagram of a power stagethat may couple between a distribution network and a high frequencytransformer. In the illustration of FIG. 15, a power stage 1500 includesan AC-DC converter 1510, a DC bus 1520 and a DC-to-high frequencyconverter 1530. As illustrated, converters 1510 and 1530 may beimplemented as H-bridge (full bridge) converters formed of a pluralityof silicon carbide (SiC) MOSFETs (namely, MOSFETs M1-M4 in AC-DCconverter 1510 and MOSFETs M5-M8 in high frequency converter 1530). Asfurther shown, DC bus 1520 may be implemented with a capacitance Cp.Note that in other embodiments, Si MOSFETs, IGBTs or Gallium Nitridepower transistors can be used instead of SiC MOSFETs, and also halfbridge or other topologies can be used.

Referring now to FIG. 16, shown is a schematic diagram of a portrectifier in accordance with an embodiment. As shown in FIG. 16, portrectifier 1600 is implemented as a passive rectifier. As shown, multipleH-bridge rectifiers each formed of a plurality of diodes (Ds1-Ds4) maybe cascaded together in series to provide a higher output voltage atoutput nodes 1610 _(A,B). As further illustrated, correspondingcapacitors Cs may be coupled in parallel to the H-bridge configurations(optionally in some cases). Understand while shown at this high level inthe embodiment of FIG. 16, many variations and alternatives arepossible.

Referring now to FIG. 17A, shown is a block diagram of a controller inaccordance with an embodiment. As shown in FIG. 17, controller 1700 maybe used to implement one or more control techniques as described herein.In this way, controller 1700 may be configured to control convertercircuitry coupled to a primary side of a high frequency transformer toresult in generation of a desired charging current and/or chargingvoltage to be supplied to dispensers to which one or more EVs maycouple. In different implementations, controller 1700 may be implementedusing general-purpose hardware such as one or more central processingunits (CPUs), microcontrollers, programmable logic devices, fieldprogrammable gate arrays (FPGAs) or so forth. In certainimplementations, such hardware circuitry alone or in combination withfirmware and/or software of an EV charging system may be used to performthe control techniques.

As illustrated in FIG. 17A, shown is an example controlled voltagecharging mode control technique. With this technique, a desired chargingvoltage may be provided as an input. In different implementations, thischarging voltage may be received as a request from charging circuitrypresent in a connected EV, or may be provided in another manner. Where afixed DC bus is supplied to multiple EV dispensers (such as in FIG.13A), the charge voltage command is a fixed value (e.g., 1000V). Inother cases, an EV charge system supplies a voltage requested by an EVbattery, and thus the charge voltage command is assigned as the EVbattery requested voltage. In one or more embodiments, feedbackinformation in the form of one or more voltages and/or currents may betransformed from a three phase A-B-C reference frame to an arbitrarytwo-phase perpendicular rotary d-q reference frame.

As illustrated in FIG. 17A, this charge voltage command is provided to afirst error circuit 1710, which also receives a measured chargingvoltage, which may be measured at output ports of the unidirectionalrectifiers. The resulting difference corresponding to an error signal isprovided to a proportional integral (PI) controller 1715. PI controller1715 generates a control output that is provided to another errorcircuit 1720. As shown, error circuit 1720 also receives a measuredcurrent, namely, an active current that may be measured at an input of agrid-side converter as three-phase currents transformed to arbitrary twophase reference frame from the d-axis. The resulting output of errorcircuit 1720 is provided to another PI controller 1725 that, in turn, iscoupled to another error circuit 1730. As shown error circuit 1730receives the d-axis component of the grid-side voltage and may alsoreceive a decoupling factor. A resulting d-axis component of voltagereference Vd* is provided to a transformation circuit 1760.

In similar manner, the q-axis component of voltage reference Vq* isgenerated and provided to transformation circuit 1760. Thus stillreferring to FIG. 17A, another path is present to accommodate decoupledcontrol of active power and reactive power. As shown in this secondpath, a first error circuit 1740 receives a reactive current command anda q-axis component of the grid-side current, with an error signal beingprovided to a PI controller 1745 that provides an output to anothererror circuit 1750, which may also receive a decoupling factor. Asshown, error circuit 1750 outputs a q-axis component of voltagereference Vq*, also provided to transformation circuit 1760.

In turn, transformation circuit 1760 may perform a d-q transformation totransform voltage and current values to the three phase A-B-C referenceframe from the arbitrary two-phase perpendicular rotary d-q referenceframe. As shown, transformation circuit 1760 outputs three-phase voltagecontrol signals V_(A)*−V_(C)* to a gate signal generator 1770 that, inturn, generates gate signals that may be provided to a grid-sideconverter 1780. Note that high frequency DC-to-AC converters may becontrolled to synchronously switch at a fixed duty cycle. Understandwhile shown with this particular implementation in FIG. 17A, manyvariations and alternatives are possible. For example, in another mode,controller 1700 may instead receive a charge current command at errorcircuit 1710 to perform a controlled current charging mode.

In yet other implementations, control techniques may be performed tocontrol charging voltage or current by appropriate control of highfrequency converters. Referring now to FIG. 17B, shown is a controllerin accordance with another embodiment. As shown in FIG. 17B, controller1701 (which may be implemented using similarly circuitry as controller1700) may be used to control a high frequency converter 1790. Asillustrated, controller 1720 similarly includes a first error circuit1710 and a PI controller 1715. Error circuit 1710 generates an errorsignal based on a received charge voltage command and a measuredcharging voltage. In turn, PI controller 1715 generates a command dutycycle that is provided to gate signal generator 1770, which generatesgate signals to provide to high frequency converter 1790.

Although shown with this particular implementation, understand that thiscontroller also may be configured for a controlled current charging modein which error circuit 1710 instead receives a charge current controlcommand and a measured charging current. In the embodiment of FIG. 17B,the DC bus voltages of the power stages may be assigned a fixed voltage(e.g., 800V). Then the port charging voltage (as in FIG. 13A) orsupplied charge voltage to EV batteries (as in FIG. 13B) is regulatedusing the duty cycle of the high frequency converters.

Referring now to FIG. 18, shown is a flow diagram of a method inaccordance with another embodiment. More specifically, method 1800 ofFIG. 18 may be performed by a controller of an EV charging system toperform charging of one or more EVs connected to the EV charging system.

As illustrated, method 1800 begins by receiving an indication ofconnection of an EV to a dispenser and charging requirements/batterystatus of the EV (block 1810). This communication may be received in thecontroller from the EV itself, namely, a charging controller of the EV.In another configuration, the EV's may communicate to a centralprogrammable logic controller (PLC) and the PLC can communicate to acharging station controller. Different communication protocols such asMODBUS, CAN BUS, Ethercat or so forth may be used.

Next at block 1820, the controller may receive a required charging level(e.g., a given charging voltage or charging current) to be supplied tothe EV. Note that in some implementations, this information may becommunicated as part of the communication of block 1810. Next at block1830, at least one of a grid-side converter or a high frequencyconverter may be controlled. More specifically, the controller may sendcontrol signals to these converters to enable the EV charging system toprovide the required charging level at an output port to which the EV isconnected (such as via a dispenser). Note that the controller mayexecute one or more algorithms to determine the appropriate controlbased on the required charging level and/or a measured chargingcurrent/voltage.

Note that the determination as to control of grid-side converter or highfrequency converter may be fixed by configuration of the EV chargingsystem or the range of required charging voltage, such that the EVcharging system may operate according to a single one of these modes orthe control modes may be switched during charging, o both control modescan be used. Or it may be possible to selectively control one of thegrid-side converters or high frequency converters based on chargingrequirements, the type of EV connected or one or more other conditions.In general by controlling the grid-side converter, a narrow range ofcharging voltages is possible (e.g., 700V to 1000V). If a lower voltageis needed, the duty cycle of the high frequency converter can becontrolled to reduce the charging voltage. Understand while shown atthis high level in the embodiment of FIG. 18, many variations andalternatives are possible.

While the present disclosure has been described with respect to alimited number of implementations, those skilled in the art, having thebenefit of this disclosure, will appreciate numerous modifications andvariations therefrom. It is intended that the appended claims cover allsuch modifications and variations.

1. An electric vehicle (EV) charging system comprising: a plurality offirst converters to receive grid power at a distribution grid voltageand convert the distribution grid voltage to at least one secondvoltage; a single high frequency transformer coupled to the plurality offirst converters to receive the at least one second voltage and tooutput at least one high frequency AC voltage; and a plurality of portrectifiers coupled to a plurality of secondary windings of the singlehigh frequency transformer, each of the plurality of port rectifierscomprising a unidirectional AC-DC converter to receive the at least onehigh frequency AC voltage and convert the at least one high frequency ACvoltage to a DC voltage, wherein at least some of the plurality of portrectifiers are coupled in series to provide at least one of a chargingcurrent or a charging voltage to at least one dispenser to which atleast one EV is to couple.
 2. The EV charging system of claim 1, furthercomprising a solid state circuit breaker to disable at least one of theplurality of port rectifiers.
 3. The EV charging system of claim 2,wherein the solid state circuit breaker comprises one or more of theplurality of first converters.
 4. The EV charging system of claim 1,further comprising a controller, wherein the controller is to disable atleast one gate signal to one or more of the plurality of firstconverters in response to detection of a fault.
 5. The EV chargingsystem of claim 1, wherein the plurality of port rectifiers comprise aplurality of passive rectifiers.
 6. The EV charging system of claim 5,further comprising a controller to control at least some of theplurality of first converters to cause the plurality of passiverectifiers to provide the at least one of the charging current or thecharging voltage.
 7. The EV charging system of claim 6, wherein theplurality of first converters each comprises a grid-side converter toconvert an AC voltage of the grid power to a DC voltage and a highfrequency converter to convert the DC voltage to a high frequency ACvoltage.
 8. The EV charging system of claim 7, wherein: in a first mode,the controller is to control the grid-side converter of the at leastsome of the plurality of first converters to cause the plurality ofpassive rectifiers to provide the at least one of the charging currentor the charging voltage; and in a second mode, the controller is tocontrol the high frequency converter of the at least some of theplurality of first converters to cause the plurality of passiverectifiers to provide the at least one of the charging current or thecharging voltage.
 9. The EV charging system of claim 1, wherein the atleast one dispenser comprises a plurality of dispensers coupled to theplurality of unidirectional rectifiers, wherein the plurality ofdispensers are to receive a fixed voltage from the plurality ofunidirectional rectifiers and provide a requested charge level to one ormore EVs.
 10. The EV charging system of claim 1, further comprising atleast one platform coupled to the EV charging system, the at least oneplatform comprising: a DC-DC converter to receive the charging voltageand output a DC charging voltage or a charging current; a plurality ofswitches coupled to the DC-DC converter; a plurality of dispensers eachcoupled to one of the plurality of switches, wherein each of a pluralityof EVs is to couple to one of the plurality of dispensers; and acontroller to selectively cause the DC charging voltage or the chargingcurrent to be provided to at least some of the plurality of dispensersin sequence.
 11. The EV charging system of claim 10, wherein thecontroller is to selectively switch the DC charging voltage or thecharging current from being provided to a first dispenser of theplurality of dispensers to being provided to a second dispenser of theplurality of dispensers in response to at least one of a temperature ofa battery of a first EV coupled to the first dispenser or a state ofcharge of the battery of the first EV reaching a threshold level. 12-17.(canceled)
 18. An electric vehicle (EV) charging system comprising: agrid-tie module comprising a plurality of grid-side converters toreceive grid power at a distribution grid voltage and convert thedistribution grid voltage to a plurality of DC voltages and a pluralityof high frequency converters to convert the plurality of DC voltages toa plurality of first high frequency AC voltages; a single high frequencytransformer having: a plurality of primary windings each coupled to oneof the plurality of high frequency converters to receive a correspondingone of the plurality of first high frequency AC voltages; and aplurality of secondary windings each to output one of a plurality ofsecond high frequency AC voltages; and a plurality of port rectifierscoupled to the plurality of secondary windings, each of the plurality ofport rectifiers comprising a unidirectional AC-DC converter to receiveone of the plurality of second high frequency AC voltages and convertthe one second high frequency AC voltage to a DC voltage, wherein atleast some of the plurality of port rectifiers are coupled together toprovide at least one of a charging current or a charging voltage; and atleast one dispenser coupled to the plurality of port rectifiers, whereinthe at least one dispenser is to provide the at least one of thecharging current or the charging voltage to at least one EV.
 19. The EVcharging system of claim 18, further comprising a controller, whereinthe controller is to control the grid-tie module to cause the at leastsome of the plurality of port rectifiers to provide the least one of thecharging current or the charging voltage to the at least one EV.
 20. TheEV charging system of claim 19, wherein the controller is to control aduty cycle of at least some of the plurality of high frequencyconverters to cause the at least some of the plurality of portrectifiers to provide the least one of the charging current or thecharging voltage to the at least one EV.
 21. The EV charging system ofclaim 18, wherein the at least one dispenser is to provide the at leastone of the charging current or the charging voltage to the at least oneEV comprising a medium duty or a heavy duty EV, to charge the at leastone EV to at least an 80% charge level within approximately 30 minutesor less.